FIG. 18 is a diagram illustrating an example of a configuration of a conventional radio base station apparatus (see CPRI Specification V2.1, for example). A radio base station apparatus 200 includes a radio equipment controller (REC) 210 for processing the baseband signal and a radio equipment (RE) 220 for processing the radio signal. The radio equipment controller 210 and the radio equipment 220 are connected to each other by an optical fiber 230. For this connection, an interface CPRI is used.
FIG. 19 is a diagram illustrating an example of a configuration of a conventional radio communication system using the CPRI (common public radio interface) as an interface (see PCT/JP2007/000565, for example). The radio communication system 100 includes a first radio base station apparatus 2, a second radio base station apparatus 4 and superordinate apparatuses 1, 3 connected to the radio base station apparatuses 2, 4, respectively. The first radio base station apparatus 2 and the second radio base station apparatus 4 are connected to each other through interface conversion units 213, 513 of radio equipment controllers 21, 51, respectively. The radio communication system 100 conducts radio communication with terminal devices through an antenna 5. The radio communication system 100 can provide two radio services A, B to the terminal devices.
The conventional radio communication system 100, however, harbors the problem that in the case where a fault occurs in the interface conversion unit 513, the signals from the second radio equipment controller 51 adapted for the radio service B and the signal from the first radio equipment controller 21 adapted for the radio service A cannot be output to a radio equipment 52. In such a case, the radio communication system 100 can not provide radio service A or B to the terminal devices continuously.